1. Technical Field
This disclosure relates generally to surgical training and demonstration apparatus. More particularly, to apparatus and methods for demonstrating and training surgeons in the detection, localization and imaging of radiation in biological systems.
2. Background of the Related Art
The detection of cancerous tissue using emissions from radionucleid labeled antibodies has been the subject of intense investigation for many years. Typically, the procedures involve the injection of radionucleid labeled antibodies into a patient. Over time, e.g. four to twenty-four hours, these labeled antibodies concentrate at tumor sites where they can be detected using sophisticated radiation detection equipment.
The particular choice of radionucleid for labeling antibodies is dependent on its nuclear properties, the physical half life, the detection instrument capabilities, the pharmacokinetics of the radiolabeled antibody and the degree of difficulty of the labeling procedure. Early techniques utilized the .sup.131 I radionucleid in conjunction with a relatively large and complex gamma camera positioned above the patient during the imaging process. This technique was less than ideal because the high energy gamma-photon emitted from .sup.131 I is not well detected by traditional gamma cameras. In addition, the administered marker emissions deliver a high radiation dose to the patient. These techniques are also deficient in that, as tumor sites become smaller, the radionucleid concentrations tend to become lost, from an imaging standpoint, in the background or blood pool radiation necessarily present in the patient.
In an effort to overcome these limitations, extensive research has been carried out in the field using much lower energy gamma emissions levels, for example, .sup.125 I (27-35 kev), in conjunction with probe-type detection structure configured for insertion into the patient's body to minimize attenuation.
This improved method of localization, differentiation and removal of cancerous tumors involves a surgical procedure wherein the patient suspected of having neoplastic tissue is administered an effective amount of a labeled antibody specific for neoplastic tissue. The antibody is labeled with a radioactive isotope exhibiting photo emissions of specific energy levels.
The surgical procedure is then delayed for a time interval to permit the labeled antibody to concentrate in the neoplastic tissue and to be cleared from normal tissue so as to increase the ratio of photon emissions from the neoplastic tissue to the background photon emissions. Once this time interval passes, the patient is surgically accessed and tissue within the operative field to be examined for neoplastic tissue is measured for a background photon emission count. Thereafter, a hand held probe is manually manipulated within the operative field adjacent tissue suspected of being neoplastic.
This procedure, commonly referred to as "radioimmuno guided surgery" or RIGS was pioneered by E. W. Martin, Jr., M. D. and M. O. Thurston, Ph.D. A more detailed presentation of RIGS is found in U.S. Pat. No. 4,782,640 to Martin and Thurston, the disclosure of which is incorporated herein by reference.
Another common procedure which makes use of radionucleid labeled antibodies is known as Lymphatic Mapping and is used in the diagnosis and treatment of e.g. skin or breast cancers. This procedure permits the surgeon to map the drainage of cancerous lesions to determine the extent and location of their expansion in the body. Radionucleid labeled antibodies are injected at the site of the known lesion and permitted to circulate with the drainage of the lesion to the lymph nodes. Thereafter, using a radiation detector, the specific lymph nodes affected by the lesion can be identified and selectively treated.
In carrying out the RIGS and lymphatic mapping procedures, the encountered radiation may be quite random and the background-to-concentration ratios may vary widely. To be used to its maximum effectiveness these procedures should be carried out by a highly trained surgeon experienced in the nuances of cancerous tissue detection. To date, surgeons have been trained using textbooks, observation and animal studies. While these are adequate to familiarize the surgeons with ideal or typical background-to-concentration readings, they are inadequate to simulate actual physiological patient conditions and, in the case of animal laboratory studies are quite expensive. Further, in animal studies neoplastic tissue is typically not inherently present, making simulation of background radiation and areas of concentration difficult at best.
Accordingly, a need exists for a surgical training/demonstration structure which can be used in training surgeons in in vivo radiation detection without the need for animal laboratory studies.